Bushing assembly for transformers and the like



Aug. 30, 1932. l. c. NICHOLS 1,873,973

BUSHING ASSEIBLY FOR TRANSFORIERS AND THB LIKE med sept. s. 1931 Patented Aug. 30, 1932 UNITED STATES PATENT; OFFICE LOUIS C. NICHOLS, OF WAUWATOSA, WISCONSIN, ASSIGNOR TO ALLIS-CHALMERS MAN- UFACTURING COMPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF DELA-- WARE RUSHING ASSEMBLY FOB TRANSFORMEBS THE LIKE Application led September 8, 1931.

This invention relates in general to elec-` trical apparatus and more in particular to an improved bushing assembly for transformers, reactors, circuit-breakers, pot-heads A and the like.

The disadvantages of the bushing assemblies known in the prior art are more apparent in a consideration of transformers of the distribution type.` In distribution transformers it is usual practice to use insulated flexible cables to make connection between the transformer windings and the external circuits, the cables usually being carried out `from a connection block through bushings fastened in pockets formed in the side walls of the transformer casing. In this construction the pockets and the bushings stick-out 0r project beyond the base and side-walls of the transformer making it diicult to pro- '20 tect the bushings during transportation and installation, moreover, broken bushings can` not be readily replaced. It is also possible for the insulating oil to siphon out through the insulation of the cables. Also this construction results in a transformer which requires considerable mor(` floor space or vault space than necessary due to the overhanging pockets, bushings, and the flexible cables.

In transformers of the power type it has 3o been general practice to mount the high and low tension bushings on the cover of the transformer by means of bolted flanges and the like, but these types of mountings cannot be used on smaller electrical apparatus such as distribution transformers on aocoun of space limitations.

It is an object of this invention to provide an improved bushing assembly which permits a bushing to be mounted on a supporting member wit-hout using bolted flanges.

Another object of this invention is to provide a bushing assembly in which the bushing is held in place on a casing member by means of a strain insulator device.

Another object of this invention is to provide an improved electrical apparatus characterized by the manner in which bushings are mounted thereon.

It is also an object of this invention to provide a bushing assembly in which the bushing Serial No. 581,600.

casing and mechanically andl electrically connected to the device.

These and other objects and advantages are attained by this invention, various novel features of which will ,be apparent from the descriptionv and drawing herein, and will be more particularly pointed out in the claims.

An illustrative exam le of the application of this invention is siiown inthe accompanying drawing in which:

Figure l is a sectional elevation of a distribution transformer showing a bushing assemblyv embodying this invention;

Fig. 2 is a side view of the transformer shown in Fig. 1 with the casing broken away so as to show the manner in which the transformer core is fastened to the casing;

Fig. 3 is an enlarged view of the strain insulator assembly shown in Fig. l; and

Fig. 4 is a viewof Fig. 3, taken at right angles thereto.

Referring now to Fig. 1, a transformer casing 5 having a bottom portion 6 is partly filled with an insulating liquid 7. A combined drain plug and oil sampling device 8 is provided near` the bottom of casing 5. A core and coil assembly is designated generally by 9 and comprises a core 10, a coil 1l having primary and secondary windings, and a plurality of high and low tension leads l2 to 1G, and a tap-changer 17. The core stack 10 is clamped together by means of a pluralclamped and welded at the rear of the core as .viewed in F ig. l. The four verticalv angle irons also serve as legs which rest on the bottom 6 of the casing and support the weight l of the core and coil assembly 9.

preferably welded. Bent members 28 and 29 are fastened preferably by welding to the horizontal angle irons 18 and 19 and serve the double purpose of lifting-eyes for untankving the transformer and of guide members which cooperate with the 'l' shaped guides 26 and 27 to center the core and coil assembly 9 in the'casing 5. A pair of clamping members 30 and 3l are provided for locking the core and coil assembly 9 to the vertical guide members 26 and 27to prevent displacement of the core and coil assembly. The above clamping members 80 and 3l are bolted to guide members 26-27 and also to members 28-v-29, and must be detached before the 'transformer can be untanled.

, lleterring again to Fig. k1, the transformer casing 5 is shown as also'provided with a eover member 32 which is held down bythe pull exerted by the strain members 45 and 45'? this cover member may be also held in place by any suitable clamps known in the art. This cover has a plurality of sleeve members 33 and 33 welded thereto which serve to support bushings 34 and 34. The cover is also provided with a hand-hole cover 52 to which a ventpipe 58 is attached. Bushings 34 and 34 carry terminal members 35 and 35", respectively, to which external circuit connections are adapted to be made by. means of lock nuts 36-36. y Interposed between the terminal members 35-35 and bushings 34-34" are suitable gaskets 37 and 37. Also interposed between l bushings 34-34 and sleeve members 38-33 are other gaskets 38 and 38which are made of any suitable material. Extending'from the terminal 'caps 35-35 through bushings 34-34 are a plurality of conductor rods 89 and 39. The lower portions of these conductor rods are threailed and carry a plurality of nuts 40 and 40 which serve as lower abutments for the busi 'ugs S34-.M342 and also serve tohold il lugs 4l and4l. It is preferable that a suitable number of spring washers 5l-51" be placed between bushings 34.--34 and nuts 4Q-40' to serve as resilient shim members. These washers, if used, permit the tension in the upper portion of the conductor rods 39--39 to be. greater than in the lower portion thereof so that the terminal caps may be firmly held in place'on the bushings without exerting too great a downward force on the cover member 32. The con ductor rods, due to their mechanical connection to the transformer core, thus exert any desired poressere tion or even all oli the clamping force necessary to hold the cover in place. Lugs 4l-41 are connected to the ends of leads l2 and l5, respectively. While the. drawing shows but one high-tension bushing 34 and one high-tension lead (l2) and but one lowf tension bushing 34', it is to be understood that there actually are more' high and low tension bushings and leans; the exact num. ber depending upon the particular use to which the transformer is designed.

Referring to Figs. 3 and 4, in connection with Fig. l, a pair of clips 42 are attached to the lower end of rod 39 by suitable connecting means such as bolt 43. Clips 42 are provided with bent-in portions 44 which are adapted to engage grooves in an insulating member 45. The upper end of this insulating member is firmly fastened in the jaws of the clip members 42 by means of a bolt 46. A pair of plates 47 are fastened to the lower end of insulating member 45 byvv means of bolt 48. A U shaped strap or clevis member 49 is connected to the lower end of member 45 by means of a pin 50 which is preterably in the form of a cotter key. The Clovis member 49 is attached to angle iron 18 preferably by welding, since this permits member 49 to be attached so as to be in alignment with the thimble member 33. VAlthough only one anchoring means. for oneconductor rod has been described, it is to be understood that there will be one anchoring means such as described for each bushing or group of bushings. Also satisfactory clamping action is obtained with the clevis members attached to other stationary parts within the casing In assembling the above described transformer, core l0, coil l1f core clamps5 clerises 49, and tap-changer l? are irst assembled to ferm the assembly generally indicated by 9; their the leads 12,15, 16, etc. from the high and low tension windings are connected to conductor rods 39--39g then the insulating members 45, etc. are attached at one end to the clevises 49 and at the other end to conductor rods 39--39i as heretofore described; then the apparatus so far assembled is lowered into casing 5, noting that guide members 2829 cooperatingvwith guide Ways will center the assembly within the casing; then locking members lO-3l are bolted into place; then the cover member 2 is slipped over the protruding conductor rods 39-39 and is clamped into place; then a suitable number of spring washers 5l-51 are slipped over the conductor rods until the distance therefrom to the surface of sleeve members 553-33" suilieient to give the bushings proper seating; then the bushings 34-34 and gaskets 38-38 are slippedover the respective conductor rods 3.9-59,etc. then gash-ets 37-37 are slipped over each conductor rod; ythen the terminal caps 35i-35" are screwed down so that both the upper parts and the ice Leraars lower portions of all the conductfm rods are under tension; then insulating oil is poured into the casing through the open hand-hole in the cover until the high tension bushing Shanks are submerged in oil; the hand-hole cover is finally fastened over the handhole.

In order to replace a faulty or broken bushing it is only necessary to disconnect the line conductor `from the terminal cap of the faulty bushing, then unscrew the terminal cap and lift out the bushing. A new bushing and gaskets may then be slipped over the conductor rod. Then the terminal cap may be screwed back in place and reconnected to the line.

It is to be understood that the disclosure herein described is merely illustrative of the invention and is not to be taken in a limiting sense; changes in details of construction and arrangement of parts being permissible so long as within the spirit of the invention and the scope of the claims which follow.

It is claimed and desired to secure byv Letters Patent:

1. A transformer having in combination, a casing provided with a cover member, a bushing mounted on said cover, and means including an insulating strain member for holding said bushing in place on said cover member.

2. A transformer having in combination, a casing provided with a cover member, a core and coil assembly clamped to said casing. a pluralitiT of bushings mounted on said cover member, terminal members on each bushing and means connecting said terminal members with said core and coil assembly for holding said bushings in place on said cover member.

3. In combination, a casing-having a perforation therein, a bushing having a shank extending through said perforation, a stationary support within said casing, and means comprising an insulated strain member attached -to said support for holding said bushing in place. i

4. In combination, a casing having acover member, an electrical device within said casing and having a. lead, a bushing extending through said cover member, a terminal mem* ber carried by said bushing, means for mechanically' connecting said terminal member to said device so as to hold said bushing in place, and means for electrically connecting said lead to said terminal member.

5. In combination, a casing having a cover member, an electrical device within said casing, means for attaching said device to said casing, a bushing extending through said cover, an electric conductor member extending through said bushing to said electrical device, and an insulating strain member connected between said conductor member and said electrical dvice to hold said bushing .in place.

6. In combination, a member having a sleeve attached thereto, a bushing supported by said sleeve and having a shank extending therethrough, a conductor extending through said bushing, and means for putt-ing said conductor under tension to hold said bushing in place on said sleeve.

7. In combination, amember having a sleeve united thereto, a bushing supported by said sleeve and having a shank extending therethrough, a conductor extending through said bushing and means including an insulating strain member connected to said conductor for holding said bushing in position on said sleeve.

8. In combination, a .member having a sleeve united thereto, a bushing supported by said sleeve and having a shank extending therethrough, a conductor extending through said bushing, lock-nuts on said conductor,

spring members between said lock-nuts and said shank, and means for putting said conductor under tension to hold saidzbushing in place on said sleeve.

9. In combination, a member having a sleeve attached thereto, a bushing supported by said sleeve and having a shank extending therethrough, a terminal member mounted on said bushing, a conductor extending from said terminal member through said bushing, lock-nuts on said conductor, spring washers between said lock-nuts and said shank, and

means including a strain insulator for holding said bushing in place on said sleeve.

10. In combination, a casing having a cover member with a plurality of openings therein, a bushing extending through each of said opcninffs and supported by said cover, a terminal cap for each of said bushings, conductor rods extending through each bushing from said terminal caps, electrical mechanism within said casing, means comprising strain insulators connected between said conductor rods and said mechanism for holding said bushings in place, and electrical connections from said mechanism to said conductor rods.

l1. In combination, a tank containing an insulating liquid, an electrical device immersed in said liquid, bushings projecting through said casing and supported thereby, conductor rods extending through said bushings, means associated with one end of said rods for providing a. resilientabutment for said bushings, terminal caps fastened to the other end of said rods whereby said bushings may be removed by unfasteningsaid terminal caps, and means connected between the first mentioned ends of said rods and said electricai device for straining said conductor rods.

l2. In a distribution transformer, the combination of, a. cover member having sleeves mounted thereon, bushings having Shanks extending through said sleeves and supported by said sleeves, terminal members on each of said bushings and means connected with said terminal members for biasing said bushings toward said sleeves.

13. In combination, a casing having side Walls and having a cover member With a plurality of openings therein, bushings extending through said openings and supported by said cover member, and means including strain insulators for biasing said bushings toward said cover member to hold said cover member in place on said side Walls.

14. In combination, a casing having side Walls and having a cover member with a plurality of openings therein, bushings extending through said openings and supported by.

said cover member, a terminal cap for each bushing, a conductor rod extending through each bushing from said terminal caps, electrical mechanism Within said casing, strain insulators connected between said conductor rods and said mechanism for exerting a force on said bushings to clamp said cover member to said side Walls.

l5. The method of assembling an electrical apparatus having a casing provided With a perforate cover member, bushings, terminal caps, Conductor rods, strain insulators, and an electrical device having leads, which comprises the steps of; connecting the leads of said device to said conductor rods; connecting said strain insulators between said device and said conductors; placing the elements so far assembled in said casing; putting said perforated cover member on said casing in such a manner that the conductor rods project through the perforations; slipping bushings over said conductor rods; and fastening said terminal caps to said conductor rods in such a manner that the bushings are urged against said cover member.

In testimony whereof, the signature of the inventor is aiixed hereto.

LOUIS C. NICHOLS. g 

